The NPC'able are items you are supposed to sell to NPC for credits, fuels are used to enhance weapons, premium oil is used as additive to reduce the credit cost to 0, Tuning components with Lv XX on them are for gears, to change tunings while keeping a slot or more the same (you won't need any if you retune everything) the 2* one is for costumes, same thing.

The NPC'able are items you are supposed to sell to NPC for credits, fuels are used to enhance weapons, premium oil is used as additive to reduce the credit cost to 0, Tuning components with Lv XX on them are for gears, to change tunings while keeping a slot or more the same (you won't need any if you retune everything) the 2* one is for costumes, same thing.